Carbon/carbon (“C/C”) parts are employed in various industries. An exemplary use for C/C parts includes using them as friction disks such as aircraft brake disks, race car brake disks, clutch disks, and the like. C/C brake disks are especially useful in such applications because of the superior high temperature capability, light weight, stable friction performance and/or other characteristics of the C/C material. In particular, the C/C material used in C/C parts such as aircraft brakes is a good conductor of heat and thus is able to dissipate heat away from the braking surfaces that is generated in response to braking. C/C material is also highly resistant to heat damage, and is thus capable of sustaining friction between brake surfaces during severe braking, without a significant reduction in the friction coefficient or mechanical failure.
C/C material is generally formed by utilizing continuous fibers, i.e., carbon fiber or oxidized polyacrylonitrile (PAN) fibers, referred to as “OPF.” Such OPF fibers are the precursors of carbonized PAN fibers and are used to fabricate a preform shape using a needle punching process. OPF fibers are layered in selected orientations into a fibrous preform of a selected geometry. Typically, two or more layers of fibers are layered onto a support and are then needled together simultaneously or in a series of needling steps. This process interconnects the horizontal fibers with a third direction (also called the z-direction). The fibers extending into the third direction are also called z-fibers. This needling process may involve driving a multitude of barbed needles into the fibrous layers to displace a portion of the horizontal fibers into the z-direction.
In typical OPF preforms used for production of aircraft brake preforms, z-fibers are created by transferring in-plane fibers into the z-direction by needling. Z-directions fibers are created due to the high elongation characteristics of the OPF. OPF maintains elongation values in the range of 12-14%. Carbon fibers on the other hand have elongation values that are typically less than 1%. Thus, needling operations do not effectively create a z-fiber; carbon fibers break well before a z-fiber is created.